1. Field of the Invention
The present invention relates to monitoring the operation and performance of fluid extraction equipment and processes from a subterranean well. More particularly, the present invention relates to systems for wirelessly monitoring dynamic performance in a sucker-rod pumped hydrocarbon well.
2. Description of the Related Art
Some wells utilize a pumping system to extract oil, gas, and water from subterranean well boreholes. Other wells rely on natural reservoir pressure, including gas pressure to extract fluids. A pumping system typically comprises a surface mounted reciprocating drive unit coupled to a submerged pump by a long steel rod, referred to as a sucker-rod. The submerged pump consists of a chamber, plunger, and a pair of check valves arranged to draw fluids into the chamber and lift fluids to the surface on each upstroke of the plunger. Wells that primarily produce gas can employ a cyclical plunger in a plunger lift arrangement that employs pressure differentials to purge liquids to the surface. Since wells range in depths to many thousand feet, the forces and pressures involved in the pumping operation are substantial. The costs of drilling, assembling, and servicing such wells are also substantial. Costs are only offset by efficient production of oil and gas products from the well. Thus, the careful attention given by operators to efficient and reliable operation of sucker-rod pumped wells over many decades of experience can be readily appreciated.
Well operators can directly access and monitor surface mounted well equipment performance by attaching certain sensors and transducers and analyzing the data they produce. It is also desirable for operators to monitor reservoir performance, however, this information is not readily accessible from the surface equipment, so specialized sensors and processing equipment are required. Wells typically employ a wellhead assembly at the top of the well borehole to seal the well fluids within a surface plumbing system. A reciprocating sucker-rod enters the wellhead assembly through a sliding seal, which requires that the rod be terminated at the surface level by a polished portion, commonly referred to as a polished rod. In a typical well, an electric motor drives the polished rod up and down through a mechanical drive arrangement. Thus, at the surface, the well equipment is accessible for operators to monitor the movement and forces on the polished rod, the power consumption characteristics of the electric drive unit, and also the pressures and temperatures in surface plumbing and the wellhead itself. In addition, the well casing and tubing string in the well borehole are accessible at the surface level. The tubing string is typically filled with well liquids and the annulus between the tubing string and the well casing are typically filled with gases down to a liquid level in the vicinity of the fluid producing geological formation, which may be thousands of feet below the surface. It is useful for operators to know the depth of this liquid level as well as certain other fluid and mechanical characteristics within the well bore. Liquid level measurements and other subterranean casing data can be gathered from the surface level using an acoustic pulse and echo sounding equipment.
Certain instruments for gathering well performance data are known in the art. Among these are movement sensors and force sensors that are connected to the reciprocating pump mechanism. Others include electric current and voltage sensors connected to the pump drive motor, tubing and casing pressure transducers, temperature probes, as well as the aforementioned acoustic sounding devices, sometimes referred to as an “echometer”. In the prior art, most of these sensors are utilized in a portable manner, being carried from well to well by technicians as they conduct various performance tests at various well sites. The prior art patents cited below give the reader a substantial background on the types of sensors and transducers used by operators and technicians. Note that a common characteristic in these disclosures is the use of wires and cables to interconnect between the sensors and a central processing unit, such as a PC computer. While electrical cables are a useful solution for interconnecting sensors and data processing devices during well testing activities, they have certain issues. First, since they must be built to rugged industrial standards, they are expensive. Cables are prone to electric and stress failures, particularly after frequent and repeated connection, storage, and reconnection cycles. They also tend to collect dirt and oil, which degrades their utility over time. It is also relatively time consuming for technicians to deploy, connect, and stow cables as they move from well to well. In addition, cables assembles are both heavy and bulky.
Significant advancements in equipment and techniques for gathering and processing surface data and generating down-hole data have been contributed by McCoy et al., and are presented in a series of patents, the teachings of which are hereby incorporated by reference. The use of an accelerometer and strain gauge in a polished rod transducer to implement a surface dynamometer have been taught. The accelerometer advancements are presented in U.S. Pat. No. 5,406,482 to McCoy et al., issued Apr. 11, 1995, for METHOD AND APPARATUS FOR MEASURING PUMPING ROD POSITION AND OTHER ASPECTS OF A PUMPING SYSTEM BY USE OF AN ACCELEROMETER, which teaches that an accelerometer is mounted on the pumping system unit to move in conjunction with the polished rod. An output signal from the accelerometer is digitized and provided to a portable computer. The computer processes the digitized accelerometer signal to integrate it to first produce a velocity data set and second produce a position data set. Operations are carried out to process the signal and produce a position trace with stroke markers to indicate positions of the rod during its cyclical operation.
The McCoy et al. advancements in the use of a strain gauge in a surface dynamometer are presented in U.S. Pat. No. 5,464,058 to McCoy et al, issued Nov. 7, 1995, for METHOD OF USING A POLISHED ROD TRANSDUCER, which teaches that a transducer is attached to the polished rod to measure deformation, i.e., the change in diameter or circumference of the rod to determine changes in rod loading. The transducer includes strain gauges, which produce output signals proportional to the change in the diameter or circumference of the rod, which occurs due to changes in load on the rod. The transducer may also include an accelerometer. The change in load on the polished rod over a pump cycle is used in conjunction with data produced by the accelerometer to calculate a down-hole pump card according to the teachings of in the prior art cited herein. The pump card showing changes in pump load is adjusted to reflect absolute rod load by determining an appropriate offset. Various ways to determine the offset are available. Since the pump plunger load is zero on the down stroke when the upper check valve, called the traveling valve, is open, the value necessary to correct the calculated minimum pump value to a zero load condition may be used as the offset. The offset can also be estimated by either a calculation of the rod weight, a predetermined rod weight measurement or an estimated load value by the operator. The teachings of the '058 are hereby incorporated by reference.
A typical well is built by drilling a borehole and installing a well casing. A tubing string is lowered into the well casing. The well fluids are pumped to the surface by a pump at the bottom, through the tubing string. Thus, there exists an annular space between the casing and the tubing. The well fluids are present in this space, and it is useful to know the liquid level of the well fluids to better understand well operations and to improve accuracy of certain measurements and calculations. In this regard, McCoy et al. have also provided further advancements in the art of measuring well casing and tubing liquid levels. These teachings are presented in U.S. Pat. No. 5,117,399 to McCoy et al., issued May 26, 1992, for DATA PROCESSING AND DISPLAY FOR ECHO SOUNDING DATA, which is directed to an echo sounding system with a acoustic gun that is mounted to the wellhead of a borehole casing. The acoustic gun produces an acoustic pulse that is transmitted down the casing or tubing. The acoustic pulse produces reflections when it strikes the tubing collars and the surface of the well fluid. A microphone detects the reflections to produce a return signal. This signal is digitized and stored. The teachings of the '399 patent are hereby incorporated by reference.
A further advancement in the use of echo sounding equipment, referred to as an “echometer”, is taught by McCoy et al, in U.S. Pat. No. 6,634,426, issued Oct. 21, 2003, for DETERMINATION OF PLUNGER LOCATION AND WELL PERFORMANCE PARAMETERS IN A BOREHOLE PLUNGER LIFT SYSTEM. The teachings of this patent are hereby incorporated by reference. This patent provides a method for measuring well performance in the case of a gas producing well that employs a pressure operated plunger lift apparatus to clear fluids out of the well, and the use of an echometer to evaluate plunger and well performance. In another patent by McCoy, and automatic echometer is taught, and this is U.S. Pat. No. 4,934,186, issued Jun. 19, 1990, for AUTOMATIC ECHO METER. This patent teaches an apparatus that enables continuous calculations of the depth of the fluid level within a well bore during a test interval. A sonic event is generated in the well bore, and the reflected sonic signals from down hole tubing collars and the fluid surface are sensed and recorded. By knowing the depth of the tubing collars, the fluid depth and speed of sound in the overlying gas can be computed. Subsequently, the apparatus generates sonic events and records the travel time for the sound to reflect off the fluid surface and return. Measurements of the actual fluid depth and sonic velocity are made at regular intervals, and interpolated between actual measurements to allow the variation in fluid level to be calculated from the measurements of travel time. The teachings of the '186 patent are hereby incorporated by reference.
Thus, is can be appreciated that there is a need in the art for a system and method for use in plunger lift and sucker-rod pumped oil and gas well industry that further assists operators and technicians in more efficiently performing on-site well performance testing and analysis.